First thoughts....
Magical Tinkering: This is a bit odd. The current version is that great either and this looks like an attempt to allow the artificer to create something useful as the need arises. That's situational and the list is meh anyway. This might reward creative players but I suspect it's missing the intended goal.
Spellcasting: This isn't significantly different, but I would point out that general spell changes can have some impact. I would also point out that the comparison to paladins and rangers I saw earlier in the thread was missing the cantrips artificers have at first level, which is more useful compared to favored enemy or lay-on-hands than magical tinkering.
I like moving Homunculus from the infusions to the spells.
Moving the homunculus into the spells removes an infusion tax to fill out bonus action options. Artillerists use bonus actions on cannons and battle smiths use bonus actions on steel defenders. That left someone like an alchemist either forced to take the infusion or go without, or look for another source. That's no longer the case.
The updated homunculus has hit point spread out better, PB bonus set by spell level, and a 30' ranged attack other artificers can make use of.
Replicate Magic Item: This seems more flexible, and given the gp value limitations of items for sale in some areas this could be an easy way to gain decent armor early now that it's created instead of infused.
Magic Item Tinker: I'm not convinced giving up a magic item is necessarily worth a spell slot. I would be inclined to remove the long rest restriction. It is nice to have a way to reclaim a spell slot when it is needed though.
Flash of Genius: I think this is another ability that could restore a single use on a short rest.
Spell Storing Item: Adding 3rd level spells to the list is a big upgrade to one of the best abilities artificers had. This also doubles as a method of transforming a weapon into a spell focus as a smaller benefit.
Soul of Artifice: This is better in one way and worse in another.
Alchemist thoughts...
Experimental elixirs being used or administered on a bonus action is useful. I don't, however, like the removal of a useful elixir for a small chance to select from the remaining list. If WotC wanted that approach I think they would have been better off to switch to a d8 roll and allow a choice on a 7 or 8, and then they can keep the transformation elixir with better odds of a choice.
That small chance takes away from the reasonable option to spend a 1st level spell slot on the transformation elixir.
2-5 elixirs is also better than 1-3 elixirs, but I think it would be better to start with more than 2.
Restorative reagents provides more temp hp for another small improvement.
I think chemical mastery is much improved. Conjured cauldron is more interesting than a use of mass cure wounds or heal. Alchemical eruption adds more damage. So an alchemist who casts acid splash under these rules is rolling the cantrip damage, adding INT modifier, and adding another 2d8 to a target in the small AoE. The wording might need a polish.
I know a lot of people don't care for the alchemist, but I like the bit of versatility it adds. The changes are generally positive in more elixirs, more temp hp, and a better damage option at higher levels. Conjured cauldron is interesting and thematic. I think alchemists have definitely improved but could use some tweaks.
Armorer thoughts...
I don't have much to say about the armorer. I think they're fairly straight forward.
Adding another armor model was definitely needed, and I think the size change is different enough catch my interest a bit in the dreadnaught armor.
Being bloodied to trigger the temp hp in the guardian armor has me wondering how often it can or will be triggered. The way it's worded it looks to me like an armorer artificer in guardian armor to spend a bonus action as often as desired as long as they're bloodied to give quite a bit of lasting power through repeat temp hp application.
I find it interesting that armor replication grants one additional magic item replication but armor modifications granted 2 extra infusions in the armor.
Perfected armor adding more damage is a step in the right direction.
Artillerist thoughts...
I suspect the tiny cannons are still going to be held in one hand. I don't believe there's much point in making them tiny otherwise. I also expect a lot of artillerists might have 10 extra fireballs at 11th level.
Deciding which cannon ability to use instead getting locked into a type of cannon is an improvement.
The reaction to explode the cannons is also better than spending an action for the amount of damage it does.
An issue I find with artillerists is the 1 hr shelf life on a cannon. That means every short rest it's gone. Every hour outside of that first hour it's gone. Every time it takes enough damage (mending is only good outside of combat) and it's gone. Trying to maintain a cannon in an adventuring day is hard on spell slots in a way arcane armor or a steel defender are not, and even elixirs last all day until they're used -- alchemists don't have elixirs disappear after an hour.
A person can get some good use out of the cannons while they are available, but players really need to be prepared to spend additional spell slots on cannons that won't be available for spells. Double firepower for 2 cannons is double spell slot expenditure to maintain those 2 cannons throughout the day.
Battle Smith thoughts...
I don't have much to say on this subclass as well. Battle smiths are also fairly straight forward.
The steel defender hasn't changed much and seem more reliant on INT bonus than PB. Steel bond looks like an improvement.
The battle smith still plays as a pet option and can use extra attack with weapons. This was and continues to be a solid option.
The steel defender does seem to have lost the vigilant trait, however, unless I'm just missing it.
